Code:
/ FX-1434 / FX-1434 / 1.0 / untmp / whidbey / REDBITS / ndp / fx / src / Net / System / Net / Cache / RequestCacheValidator.cs / 1 / RequestCacheValidator.cs
/*++ Copyright (c) Microsoft Corporation Module Name: RequestCacheValidator.cs Abstract: The file specifies the contract for plugged cache validation logic. Author: Alexei Vopilov 21-Dec-2002 Revision History: Aug 25 2003 - Moved into a separate file and implemented Whidbey M3 changes Jan 25 2004 - Changed the visibility of the class from public to internal. --*/ namespace System.Net.Cache { using System; using System.Diagnostics; using System.Text; using System.IO; using System.Collections.Specialized; using System.Threading; // // We need Undefined value because sometime a cache entry does not provide a clue when it should expire // not flags! internal enum CacheFreshnessStatus { Undefined = 0, Fresh = 1, Stale = 2 } // // These are valus that can be returned from validation methods. // Most validation methods can only return a subset of below values. // // not flags! internal enum CacheValidationStatus { DoNotUseCache = 0, //Cache is not used for this request and response is not cached. Fail = 1, //Fail this request (allows a protocol to generate own exception) DoNotTakeFromCache = 2, //Don't used caches value for this request RetryResponseFromCache = 3, //Retry cache lookup using changed cache key RetryResponseFromServer = 4, //Retry this request as the result of invalid response received ReturnCachedResponse = 5, //Return cached response to the application CombineCachedAndServerResponse = 6, //Combine cached and live responses for this request CacheResponse = 7, //Replace cache entry with received live response UpdateResponseInformation = 8, //Update Metadata of cache entry using live response headers RemoveFromCache = 9, //Remove cache entry referenced to by a cache key. DoNotUpdateCache = 10, //Do nothing on cache update. Continue = 11 //Proceed to the next protocol stage. } ////// internal abstract class RequestCacheValidator { internal WebRequest _Request; internal WebResponse _Response; internal Stream _CacheStream; private RequestCachePolicy _Policy; private Uri _Uri; private String _CacheKey; private RequestCacheEntry _CacheEntry; private int _ResponseCount; private CacheValidationStatus _ValidationStatus; private CacheFreshnessStatus _CacheFreshnessStatus; private long _CacheStreamOffset; private long _CacheStreamLength; private bool _StrictCacheErrors; private TimeSpan _UnspecifiedMaxAge; /*-------------- public members -------------*/ internal abstract RequestCacheValidator CreateValidator(); /* // Consider removing. protected RequestCacheValidator(): this(false, TimeSpan.FromDays(1)) { } */ protected RequestCacheValidator(bool strictCacheErrors, TimeSpan unspecifiedMaxAge) { _StrictCacheErrors = strictCacheErrors; _UnspecifiedMaxAge = unspecifiedMaxAge; _ValidationStatus = CacheValidationStatus.DoNotUseCache; _CacheFreshnessStatus = CacheFreshnessStatus.Undefined; } //public internal bool StrictCacheErrors { get {return _StrictCacheErrors;} } // // This would help cache validation when the entry does // not have any expiration mechanism defined. //public internal TimeSpan UnspecifiedMaxAge { get {return _UnspecifiedMaxAge;} } /*------------- get-only protected properties -------------*/ protected internal Uri Uri {get {return _Uri;}} protected internal WebRequest Request {get {return _Request; }} protected internal WebResponse Response {get {return _Response; }} protected internal RequestCachePolicy Policy {get {return _Policy; }} protected internal int ResponseCount {get {return _ResponseCount;}} protected internal CacheValidationStatus ValidationStatus {get {return _ValidationStatus;}} protected internal CacheFreshnessStatus CacheFreshnessStatus {get {return _CacheFreshnessStatus;}} protected internal RequestCacheEntry CacheEntry {get {return _CacheEntry;}} /*------------- protected methods and settable protected properties ------------*/ protected internal Stream CacheStream { get {return _CacheStream;} set {_CacheStream = value;} } // protected internal long CacheStreamOffset { get {return _CacheStreamOffset;} set {_CacheStreamOffset = value;} } // protected internal long CacheStreamLength { get {return _CacheStreamLength;} set {_CacheStreamLength = value;} } // protected internal string CacheKey { get {return _CacheKey;} /* // Consider removing. set { // Security: Setting a cache key would allow reading an arbitrary cache location //new RequestCachePermission(RequestCacheActions.CacheReadWrite, value).Demand(); _CacheKey = value; } */ } // /*-------------- protected virtual methods -------------*/ // protected internal abstract CacheValidationStatus ValidateRequest(); // protected internal abstract CacheFreshnessStatus ValidateFreshness(); // protected internal abstract CacheValidationStatus ValidateCache(); // protected internal abstract CacheValidationStatus ValidateResponse(); // protected internal abstract CacheValidationStatus RevalidateCache(); // protected internal abstract CacheValidationStatus UpdateCache(); // protected internal virtual void FailRequest(WebExceptionStatus webStatus) { if(Logging.On)Logging.PrintError(Logging.RequestCache, SR.GetString(SR.net_log_cache_failing_request_with_exception, webStatus.ToString())); if (webStatus == WebExceptionStatus.CacheEntryNotFound) throw ExceptionHelper.CacheEntryNotFoundException; else if (webStatus == WebExceptionStatus.RequestProhibitedByCachePolicy) throw ExceptionHelper.RequestProhibitedByCachePolicyException; throw new WebException(NetRes.GetWebStatusString("net_requestaborted", webStatus), webStatus); } /*-------------- internal members -------------*/ // internal void FetchRequest(Uri uri, WebRequest request) { _Request = request; _Policy = request.CachePolicy; _Response = null; _ResponseCount = 0; _ValidationStatus = CacheValidationStatus.DoNotUseCache; _CacheFreshnessStatus = CacheFreshnessStatus.Undefined; _CacheStream = null; _CacheStreamOffset = 0L; _CacheStreamLength = 0L; if (!uri.Equals(_Uri)) { // it's changed from previous call _CacheKey = uri.GetParts(UriComponents.AbsoluteUri, UriFormat.Unescaped); } _Uri = uri; } // internal void FetchCacheEntry(RequestCacheEntry fetchEntry) { _CacheEntry = fetchEntry; } internal void FetchResponse(WebResponse fetchResponse) { ++_ResponseCount; _Response = fetchResponse; } internal void SetFreshnessStatus(CacheFreshnessStatus status) { _CacheFreshnessStatus = status; } internal void SetValidationStatus(CacheValidationStatus status) { _ValidationStatus = status; } } }/// This class reserves a pattern for all WebRequest related cache validators. /// All exposed protected methods are virtual. /// If a derived class method does not call the base method implementation, /// then the base class context may not be updated so it's recommended suppressing the base /// methods for all subsequent calls on this class. /// ///
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